The invention relates to blown fuse detectors of the general type which monitor the voltage across a fuse, and provide a remote indication that the fuse has “blown” when the monitored voltage exceeds the small voltage drop across the fuse which occurs during normal operation when the fuse is intact. Embodiments of the invention in particular are applicable to medium voltage AC fuse circuits, operating within the approximate voltage range 2,400 to 38,000 volts.